TSYtiux. 299 



worm or small larva seemis immediately to succumb to the powers 

 of tlie Hydra's sting, but a Cyclops or Daphnia will, with a few 

 struggles, make some show of resistance, the shell, or carapace, 

 of the tiny crustaceans in their case afEording a slight pro- 

 tection against the effects of the captor's poison. 



While in confinement, the Hydrse may be fed upon such 

 Bntomostraca as the Cyclops and Daphnise, which may be 

 bred in a separate vessel for the purpose. The polypes expel 

 the indigestible parts of these small criistacea. Though the 

 Hydrse very often kill more animals than they are able to 

 eat, the dead bodies of the victims need not be removed 

 from the water, for the Entomostraca, if present in the tank 

 in amy numbers, will act the part of scavengers, and help 



Fig. 170. Uyorm attached to a piece of Anacharis Plant. 



to keep the water pure. A clear and thin glass tumbler 

 makes a very suitable little aquarium for the Hydrse, which 

 of course should have no other companions than those they 

 feed upon. They ought to be provided with some aquatic 

 plant, to which they can aS&x themselves (Fig. 170) if they 

 choose. A little duckweed, or a small spray of the water- 

 thyme {Anacharis alsinastrum) will answer the purpose very 

 well. The Hydrse, however, frequently fasten themselves to 

 the sides of the aquarium, thus much facilitating the observa- 

 tion of their habits. Hydrae increase both by gei-mination 

 aiid by being hatched from eggs. The former manner of 

 reproduction seems to be commoner than the latter. The 

 budding takes place on any part of the creature's body 

 except the tentacles. When a polype is about to produce 



